Multi-stage bubble-column vapor mixture condensation

ABSTRACT

A multi-stage bubble-column vapor mixture condenser comprises at least a first stage and a second stage. Each stage includes a carrier-gas inlet and a carrier-gas outlet, as well as a condenser chamber containing a condensing bath in fluid communication with the carrier-gas inlet and the carrier-gas outlet. The carrier-gas inlet is positioned to bubble carrier gas from the carrier-gas inlet up through the condensing bath, overcoming a hydrostatic head of the condensing bath. The carrier-gas outlet is positioned with an opening for carrier-gas extraction above the condensing bath, wherein the first-stage carrier-gas outlet is in fluid communication with the carrier-gas inlet of the second stage to facilitate flow of the carrier gas through the condensing bath in the condenser chamber of the first stage and then through the condensing bath in the condenser chamber of the second stage.

RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 15/167,585,filed 27 May 2016, which is a continuation of U.S. application Ser. No.14/744,907, filed 19 Jun. 2015, now U.S. Pat. No. 9,403,104 B2, which isa continuation of U.S. application Ser. No. 13/241,907, filed 23 Sep.2011, now U.S. Pat. No. 9,072,984 B2, the entire contents of both ofwhich are incorporated herein by reference.

BACKGROUND

In this century, the shortage of fresh water will surpass the shortageof energy as a global concern for humanity, and these two challenges areinexorably linked, as explained in the “Special Report on Water” in the20 May 2010 issue of The Economist. Fresh water is one of the mostfundamental needs of humans and other organisms; each human needs toconsume a minimum of about two liters per day. The world also facesgreater freshwater demands from farming and industrial processes.

The hazards posed by insufficient water supplies are particularly acute.A shortage of fresh water may lead to a variety of crises, includingfamine, disease, death, forced mass migration, cross-regionconflict/war, and collapsed ecosystems. Despite the criticality of theneed for fresh water and the profound consequences of shortages,supplies of fresh water are particularly constrained. 97.5% of the wateron Earth is salty, and about 70% of the remainder is locked up as ice(mostly in ice caps and glaciers), leaving only a fraction of all wateron Earth as available fresh (non-saline) water.

Moreover, the earth's water that is fresh and available is not evenlydistributed. For example, heavily populated countries, such as India andChina, have many regions that are subject to scarce supplies. Furtherstill, the supply of fresh water is often seasonally inconsistent.Meanwhile, demands for fresh water are tightening across the globe.Reservoirs are drying up; aquifers are falling; rivers are dying; andglaciers and ice caps are retracting. Rising populations increasedemand, as do shifts in farming and increased industrialization. Climatechange poses even more threats in many regions. Consequently, the numberof people facing water shortages is increasing. Naturally occurringfresh water, however, is typically confined to regional drainage basins;and transport of water is expensive and energy-intensive.

On the other hand, many of the existing processes for producing freshwater from seawater (or to a lesser degree, from brackish water) requiremassive amounts of energy. Reverse osmosis (RO) is currently the leadingdesalination technology. In large-scale plants, the specific electricityrequired can be as low as 4 kWh/m³ at 30% recovery, compared to thetheoretical minimum of around 1 kWh/m³; smaller-scale RO systems (e.g.,aboard ships) are less efficient.

Other existing seawater desalination systems includethermal-energy-based multi-stage flash (MSF) distillation, andmulti-effect distillation (MED), both of which are energy- andcapital-intensive processes. In MSF and MED systems, however, themaximum brine temperature and the maximum temperature of the heat inputare limited in order to avoid calcium sulphate precipitation, whichleads to the formation of hard scale on the heat transfer equipment.

Humidification-dehumidification (HDH) desalination systems include ahumidifier and a dehumidifier as their main components and use a carriergas (e.g., air) to communicate energy between the heat source and thebrine. In the humidifier, hot seawater comes in direct contact with dryair, and this air becomes heated and humidified. In the dehumidifier,the heated and humidified air is brought into (indirect) contact withcold seawater and gets dehumidified, producing pure water anddehumidified air. Some of the present inventors were also inventors onthe following patent applications that include additional discussionrelating to HDH processes for purifying water: U.S. application Ser. No.12/554,726, filed 4 Sep. 2009 ; U.S. application Ser. No. 12/573,221,filed 5 Oct. 2009 ; and U.S. application Ser. No. 13/028,170, filed 15Feb. 2011 .

An approach from the University of Florida, which is described in U.S.Pat. No. 6,919,000 B2, reduced the thermal resistance associated withincondensable gases by using a direct-contact condenser instead of astandard, indirect contact dehumidifier. This method increases the heattransfer rates in the condenser at the expense of energy efficiency, asthe energy from the humid air entering the dehumidifier is not directlyrecovered to preheat the seawater. Thus, although the cost of thedehumidification device is reduced, energy costs increase.

SUMMARY

Single-stage and multi-stage bubble-column vapor mixture condensers(referred to simply as a condenser elsewhere herein) andhumidification-dehumidification (HDH) systems and the operation thereofare described herein. Various embodiments of the apparatus and methodsmay include some or all of the elements, features and steps describedbelow.

A multi-stage bubble-column vapor mixture condenser comprises at least afirst stage and a second stage. Each stage includes a carrier-gas inletand a carrier-gas outlet, as well as a condenser chamber containing acondensing bath in fluid communication with the carrier-gas inlet andthe carrier-gas outlet. The carrier-gas inlet is positioned to bubblecarrier gas from the carrier-gas inlet up through the condensing bath,overcoming a hydrostatic head of the condensing bath. The carrier-gasoutlet is positioned with an opening for carrier-gas extraction abovethe condensing bath, wherein the first-stage carrier-gas outlet is influid communication with the carrier-gas inlet of the second stage tofacilitate flow of the carrier gas through the condensing bath in thecondenser chamber of the first stage and then through the condensingbath in the condenser chamber of the second stage.

The multi-stage bubble-column condenser can be coupled with a humidifierin a humidification-dehumidification system.

The apparatus and methods can be used to separate pure water from aliquid mixture (including but not limited to seawater, brackish waterand waste water) in a cost-efficient manner, which can result insubstantially reduced costs compared with previous approaches.Embodiments of the apparatus and methods can offer numerous advantages.First, based on data for bubble columns given in open literature, theheat-transfer coefficient in the multi-stage bubble-column condenser isestimated to be 7 kW/m²·K (i.e., at least one order of magnitude higherthan the current state-of-art). This heat-transfer coefficient iscomparable to, if not higher than, film condensation of steam. Second,the high energy recovery can be maintained using a novel multi-stagingtechnique. Third, multi-extraction can be employed in the apparatus andmethods to further increase heat recovery. Fourth, the overall cost ofthe system is reduced as the energy cost and the equipment cost are bothreduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional illustration of a single-stage bubble-columncondenser.

FIG. 2 is a schematic illustration of an embodiment of ahumidification-dehumidification water-purification system including amulti-stage bubble-column condenser.

FIG. 3 plots the temperature profile across columns in a multi-stagebubble-column condenser from the top of the bubbling columns.

FIG. 4 plots the temperature profile in a single-stage bubble-columncondenser from the top of the bubbling column.

FIG. 5 is a schematic illustration of an embodiment of amulti-extraction humidification-dehumidification water-purificationsystem including a multi-stage bubble-column condenser.

FIG. 6 is a sectional illustration of a bubble-column condenser orientedan angle to the vertical.

In the accompanying drawings, like reference characters refer to thesame or similar parts throughout the different views; and apostrophesare used to differentiate multiple instances of the same or similaritems sharing the same reference numeral. The drawings are notnecessarily to scale, with emphasis instead being placed uponillustrating particular principles, discussed below.

DETAILED DESCRIPTION

The foregoing and other features and advantages of various aspects ofthe invention(s) will be apparent from the following, more-particulardescription of various concepts and specific embodiments within thebroader bounds of the invention(s). Various aspects of the subjectmatter introduced above and discussed in greater detail below may beimplemented in any of numerous ways, as the subject matter is notlimited to any particular manner of implementation. Examples of specificimplementations and applications are provided primarily for illustrativepurposes.

Unless otherwise defined, used or characterized herein, terms that areused herein (including technical and scientific terms) are to beinterpreted as having a meaning that is consistent with their acceptedmeaning in the context of the relevant art and are not to be interpretedin an idealized or overly formal sense unless expressly so definedherein. For example, if a particular composition is referenced, thecomposition may be substantially, though not perfectly pure, aspractical and imperfect realities may apply; e.g., the potentialpresence of at least trace impurities (e.g., at less than 1 or 2% byweight or volume) can be understood as being within the scope of thedescription; likewise, if a particular shape is referenced, the shape isintended to include imperfect variations from ideal shapes, e.g., due tomachining tolerances.

Although the terms, first, second, third, etc., may be used herein todescribe various elements, these elements are not to be limited by theseterms. These terms are simply used to distinguish one element fromanother. Thus, a first element, discussed below, could be termed asecond element without departing from the teachings of the exemplaryembodiments.

Spatially relative terms, such as “above,” “below,” “left,” “right,” “infront,” “behind,” and the like, may be used herein for ease ofdescription to describe the relationship of one element to anotherelement, as illustrated in the figures. It will be understood that thespatially relative terms, as well as the illustrated configurations, areintended to encompass different orientations of the apparatus in use oroperation in addition to the orientations described herein and depictedin the figures. For example, if the apparatus in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the exemplary term, “above,” may encompass both an orientation ofabove and below. The apparatus may be otherwise oriented (e.g., rotated90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

Further still, in this disclosure, when an element is referred to asbeing “on,”“connected to” or “coupled to” another element, it may bedirectly on, connected or coupled to the other element or interveningelements may be present unless otherwise specified.

The terminology used herein is for the purpose of describing particularembodiments and is not intended to be limiting of exemplary embodiments.As used herein, singular forms, such as “a” and “an,” are intended toinclude the plural forms as well, unless the context indicatesotherwise. Additionally, the terms, “includes,” “including,” “comprises”and “comprising,” specify the presence of the stated elements or stepsbut do not preclude the presence or addition of one or more otherelements or steps.

The presence of incondensable gases can drastically increase the thermalresistance associated with film condensation of steam on a cold surface.For the typical mole fraction (about 70%) of air (incondensable gas)present in a dehumidifier (condenser) of ahumidification-dehumidification system, the heat-transfer coefficientcan be as low as 1/100th of that for pure steam condensation (inmulti-effect-distillation and multi-stage-flash systems). In absolutevalue, the heat-transfer coefficient can be as low as 10 W/m²·K. Hence,it is advantageous to reduce the thermal resistance associated with theincondensable gas, while at the same time preserving the advantageousincrease in energy efficiency brought about by the methods described inthe inventors' previous patent applications, noted in the Background.

A sectional view of an embodiment of a single-stage bubble-columncondenser 12 is provided in FIG. 1. The bubble column 14 contains a bathof a liquid 15 (e.g., distilled water in this embodiment). The liquid 15is supported on a bubble generator 44 inside the bubble-column chamber.Gas chambers 17 and 19 are respectively positioned below and above theliquid. Chamber 17 below the liquid allows a moist carrier gas to bepumped from conduit 32′ via a compressor/blower 34 through orifices inthe bubble generator 44 into the liquid 15 in the form of bubbles 21,though the lower chamber 17 can be omitted where the bubble generator 44includes a network of perforated pipes through which the carrier gas ispumped. A tube coil 20 that is coupled with a fluid source (e.g., seawater) snakes through the water 15 in the condenser 12, allowing forheat transfer from the water 15 in the chamber to the sea water beingdirected through the tube coil 20. Accordingly, cool fluid enters thetube coil 20 at the lower left and exits as heated fluid at the upperright. After passing through the liquid 15, the dry carrier gas collectsin the gas chamber 19 at the top of the chamber and is extracted throughgas conduit 32″.

The bubble generator 44 can have a diameter, e.g., of 1.25 m, and canhave a plurality of orifices, each having a diameter, e.g., of 1 mm forgenerating bubbles of approximately the same diameter. The bubblegenerator 44 can be in the form of, for example, a sieve plate, whereinthe carrier gas is pumped through the orifices in the sieve plate.Alternatively, the bubble generator 44 can be in the form of a spargerwith perforated pipes for distributing the carrier gas, wherein thesparger distributes the bubbles through the perforated pipes, which canextend from a central conduit. The perforated pipes in the sparger canfeature, e.g., a radial, multiple-concentric-ring, spider-web, orhub-and-spoke wheel-type configuration of the perforated pipes throughwhich the carrier gas is pumped from an external source.

As shown in FIG. 6, all components of the bubble column (e.g., all wallsand the bubble generator) can be oriented at an angle to the vertical,α, between 0° and 60° with respect to vertical (e.g., with respect to anaxis along a radian passing through the center of the earth). As thebubble column 14 is oriented at an angle, the hydrostatic head reducesfrom ρgH to ρgH·(cos α), where ρ is density (kg/m³), g is gravitationalacceleration (9.81 m/s²), and h is the height of the liquid in thecolumn. This reduction in hydrostatic head comes with a reduction influid pressure drop of up to 50%. This pressure drop, however, will comewith a reduction in the fluid-side heat transfer coefficient at higherangles (α>45°). This is because, at higher angles, the liquidcirculation will not be set up in a regular manner. However, foroptimized design, the angled configuration with lesser pressure drop mayprovide significant savings in energy cost.

An embodiment of a multi-stage bubble-column condenser in ahumidification-dehumidification (HDH) water purifier system 10 is shownin FIG. 2, wherein the dehumidifier is a multi-stage, bubble-column,vapor mixture condenser (also referred to as a “bubbler”) 12 instead ofusing an indirect-contact heat exchanger (as is common with conventionalHDH systems) to dehumidify moist carrier gas (e.g., moist air) andproduce fresh liquid water efficiently. The carrier gas is humidifiedwith vaporized water from a liquid composition (e.g., sea water or wastewater) in the humidifier 24; and the water vapor entrained in thecarrier gas is then transported via conduit 32′ to the bubble-columncondenser 12, where the water in the moist air is condensed to producefresh (i.e., substantially pure) water.

The liquid composition (e.g., sea water) is provided from a source 16(e.g., a tank) and circulated through the system by a pump 36, which canmounted in the conduit 18 between the source 16 and the bubble-columncondenser 12. The liquid composition is passed through each stage 14 ofthe condenser 12 via internal conduits 20 mounted in each stage 14,wherein the design of each of the stages 14 can substantially match thatof the single-stage bubble column of FIG. 1. In this embodiment, theliquid composition is passed between stages 14 via adjoining externalconduits 18 to preheat the liquid composition. The internal conduits 20can have thermally conductive surfaces (e.g., fins) 23 extending fromthe conduits 20 (as shown in FIG. 2) to increase the heat transfer fromthe liquid in the stages 14 to the liquid composition passing throughthe tube coil 20. After exiting the internal tube coil 20 in the bottom(first) stage 14′ of the bubble-column condenser 12, the liquidcomposition passes through an additional conduit 18 to a heater 22(e.g., a solar water heater or a waste-heat source) that further heatsthe liquid composition (e.g., to 80° C.) before the liquid compositionis passed into the humidifier 24 and atomized and dispersed via a nozzle26.

Inside the humidifier, packing material 28 is provided in the form,e.g., of polyvinyl chloride (PVC) packing to facilitate the gas flow andto increase the liquid surface area that is in contact with the carriergas to increase the portion of the vaporizable liquid that is vaporizedinto the carrier gas. The body of the humidifier 24 (and thedehumidifier 12 as well as the conduits 18 and 32) can be formed, e.g.,of stainless steel and is substantially vapor impermeable In oneembodiment, the humidifier 24 is substantially cylindrical with a heightof about 2.5 m and a radius of about 0.5 m.

The humidifier 24 and dehumidifier 12 are both of a modular construction(i.e., each in the form of a separate and discrete device) and aresubstantially thermally separated from one another. The characterizationof the humidifier 24 and dehumidifier 12 as being “substantiallythermally separated” is to be understood as being structured for littleor no direct conductive thermal energy transfer through the apparatusbetween the humidifier 24 and the dehumidifier 12, though thischaracterization does not preclude a mass flow carrying thermal energy(via gas and/or liquid flow) between the chambers. This “substantialthermal separation” characterization thereby distinguishes the apparatusfrom, e.g., a dewvaporation apparatus, which includes a sharedheat-transfer wall between the humidifier and dehumidifier. In theapparatus of this disclosure, the humidifier 24 and dehumidifier 12 neednot share any common walls that would facilitate conductive heattransfer there between.

The carrier gas flows upward through the chamber defined by thehumidifier 24 from the port for conduit 32″″ to the port for conduit32′, where it exits with a higher content of vaporized liquid.Humidification of the carrier gas is achieved by spraying the liquidcomposition from one or more nozzles 26 at the top of the humidifier 24down through a zone including packing material 28, where some of thewater in the liquid composition will evaporate, while a non-evaporatedremnant of the liquid composition (e.g., brine) flows down through arain zone to the base of the chamber defined by the humidifier 24, wherethe brine is drained via a conduit 18 into a brine-collection tank 30.Meanwhile, the carrier gas moves up through the humidifier 24 and isbrought into contact with the liquid composition, particularly in thebed of packing material 28, to humidify the carrier gas with water vaporevaporated from the liquid composition. The carrier gas can consequentlybe saturated with water vapor before being withdrawn from the humidifier24 via conduit 32′ and pumped via a compressor/blower 34 through theinlet of a first stage 14′ of the multi-stage bubble column condenser12. In particular embodiments, an air heater and/or an air compressor orthermal vapor compressor can be mounted in conduit 32′ to heat and/orcompress the carrier gas before it is pumped into the dehumidifier 12.Where an air compressor or thermal vapor compressor is mounted inconduit 32′, a complimentary air expander can be mounted in conduit 32″″to expand the carrier gas, as it is circulated back to the humidifier24. In other embodiments, the compressor/blower 34 can be positioned inthe conduit 32″″ leading to the humidifier 24 because of operationalconsiderations.

The flow of seawater through the tube coil 20 inside the dehumidifier 12can ensure that the heat is directly recovered to preheat the liquidcomposition (e.g., sea water in this embodiment) during the condensationprocess. The bubble-column condenser 12 includes a plurality of stages14, each filled with a bath of liquid (e.g., distilled water) throughwhich moist, hot carrier gas is passed using a compressor/blower 34 anda bubble generator 44 that injects gas bubbles (or through which bubblesare injected) into the bath.

The hot water-vapor-laden carrier gas emitted from the humidifier(evaporator) 24 passes (e.g., at a temperature of 70° C.) through theconduit 32′ extending from the top of the humidifier 24 and is bubbledthrough each of the stages 14 in the dehumidifier 12, where the carriergas is cooled and dehumidified. The carrier gas collects at the top ofeach stage 14 and is passed from an outlet atop each stage 14 via aconduit 32 into and through an inlet of the next stage 14 and throughthe bubble generator 44, which generates bubbles of the carrier gas thatthen pass through the distilled water in the stage 14, and the carriergas is then again collected at the top of the column. This process issequentially repeated in each subsequent column.

A low pressure drop in the present dehumidifier 12 can keep pumpingpower low, thereby enabling an economically feasible system. This focuson maintaining low pumping power is in contrast to many bubble columnsin the chemical industry, where the primary concern is heat and masstransfer, and where pressure drop may not be a significant designconstraint. Pressure drop in the bubble chamber in each stage 14 occurslargely due to the following three factors: (1) head loss at the bubblegenerator 44, where bubbles are generated, (2) friction between thecarrier gas and the distilled water as the bubbles rise through theliquid, and (3) the hydrostatic head. As the hydrostatic head is thelargest contributor to total pressure drop across a given stage 14, theheight of each stage 14 (measured vertically in the orientation shown inthe Figures) is advantageously kept low. To obtain a pressure drop lowerthan 1 kPa, for example, the total height of all the stages 14 sum toless than about 1 m. Typically, this height constraint manifests itselfin the form of a low-aspect-ratio bubble column, where the ratio ofcolumn height to diameter (measured horizontally in the orientationshown) is less than 1. In particular embodiments, the diameter of thecolumn is 0.5 to 1 m, while the height of the column is 0.05 to 0.1 m(for an aspect ratio of the column of about 0.1).

The temperature of the carrier gas can drop at least 5° C. from eachstage to 14 the next in the humidifier 12, as it is cooled by the liquidbath in each stage 14. For example, in the conduit 32″ from the outletof the first stage 14′ to the inlet of the second stage 14″, the carriergas can have a temperature, e.g., of about 60° C., while the carrier gasin the conduit 32″′ from the outlet of the second stage 14″ to the inletof the third stage 14″′ can have a reduced temperature, e.g., of about50° C. When the carrier gas exits the bubble-column condenser 12 throughthe top conduit 32″″, the carrier gas circles back to the bottom of thehumidifier 24 (with a reduced content of the vaporizable liquid), itstemperature can be further reduced to, e.g., about 30° C. In the initialtransient period during process startup, water vapor in the hot-humidcarrier gas transmits the latent heat to the water in each stage 14 (inwhich a natural circulation loop is established); and a mixed averagetemperature of the water stage 14 is eventually achieved at steadystate. Once steady state is achieved, the heat of condensation isdirectly extracted by seawater that is sent through the coiled tube 20.Thus, direct heat recovery is achieved.

Where the condensed vapor is water, the dehumidification of the carriergas in each stage 14 releases water from the carrier gas to thedistilled water through which carrier gas is bubbled. The water isdrained from each stage 14 (equivalent to the water increase provided bythe dehumidification of the carrier gas) through conduits 38 to apure-water collection tank 40. Alternatively, the liquid (e.g., water)can be extracted via a conduit from the bath in the third stage 14″′ andpassed to the lower-temperature second stage 14″ and extracted viaanother conduit from the second-stage 14″ and passed to thestill-lower-temperature first stage 14′, from which it is finallyextracted from the multi-stage, bubble-column condenser 12 as product.

Though a single stage/column 14 can be used, the use of multiple stagesin the bubble-column condenser 12 pushes the temperature to which theseawater is preheated toward the maximum possible (which is thetemperature of the carrier gas inlet). The effects of this staging canbe clearly understood via the temperature profiles in a multi-stagebubble-column condenser (shown in FIG. 3) and in a single-stagebubble-column condenser (shown in FIG. 4), where the seawater exittemperature can be seen to be much higher in the plots for themulti-stage bubble-column condenser, as shown in FIG. 3. Each of theplotted horizontal segments 46 (˜308 K), 48 (˜318 K), 50 (˜327 K), 52(˜335 K), 54 (˜342 K), 56 (˜348 K) in FIG. 3 represents the temperaturein a respective column/stage 14 in a six-stage bubble-column condenser,where the horizontal axis of the chart represents non-dimensionaldistance from the top to the bottom of the bubble-column condenser 12(i.e., reference line 46 represents the temperature of the top-moststage 14). The diagonal line 58 represents the temperature of theseawater as it flows through the bubble-column condenser 12 as afunction of distance from the top of the bubble-column condenser 12.Meanwhile, the temperature 60 in the single-stage, bubble-columncondenser (shown in FIG. 4) is seen to be substantially constant (at 323K) throughout the bubble-column condenser and approximately equal to theaverage of the inlet and the outlet carrier gas temperatures.

The multi-stage bubble-column condenser 12, additionally, presents adirect advantage of enabling extraction/injections of seawater fromin-between the bubble-column stages via intermediate exchange conduits42, as shown in FIG. 5, where the intermediate exchange conduits 42 arecoupled with the bubble-column condenser 12 between the first and secondstages 14′ and 14″ and between the second and third stages 14″ and 14″′of a three-stage bubble-column condenser system. Saline water iscollected in intermediate trays 43′ and 43″ at respective intermediatestages in the chamber of the humidifier 24 and injected into theexternal conduits 18 through which the sea water flows between stages14′ and 14″ and between stages 14″ and 14″′, respectively. In otherembodiments, the direction of injection/extraction can be reversed(e.g., saline water can be extracted from the condenser 12 and injectedinto the humidifier 24), depending on the conditions of operation. Suchextraction flows can enable construction of systems that arethermodynamically balanced. In additional embodiments, the moist carriergas can be extracted/injected instead of extracting/injecting salinewater. Owing to the higher heat-transfer coefficients in a bubble-columncondenser and a lower terminal temperature difference, the apparatusdescribed herein (such as the one shown in FIG. 5) can provide superiorperformance in terms of dehumidification and the efficiency thereof.

In describing embodiments of the invention, specific terminology is usedfor the sake of clarity. For the purpose of description, specific termsare intended to at least include technical and functional equivalentsthat operate in a similar manner to accomplish a similar result.Additionally, in some instances where a particular embodiment of theinvention includes a plurality of system elements or method steps, thoseelements or steps may be replaced with a single element or step;likewise, a single element or step may be replaced with a plurality ofelements or steps that serve the same purpose. Further, where parametersfor various properties are specified herein for embodiments of theinvention, those parameters can be adjusted up or down by 1/100^(th),1/50^(th), 1/20^(th), 1/10^(th), ⅕^(th), ⅓^(rd), ½, ⅔^(rd), ¾^(th),⅘^(th), 9/10^(th), 19/20^(th), 49/50^(th), 99/100^(th), etc. (or up by afactor of 1, 2, 3, 4, 5, 6, 8, 10, 20, 50, 100, etc.), or by rounded-offapproximations thereof, unless otherwise specified. Moreover, while thisinvention has been shown and described with references to particularembodiments thereof, those skilled in the art will understand thatvarious substitutions and alterations in form and details may be madetherein without departing from the scope of the invention (for example,the condensed liquid can be a composition other than water; more orfewer stages can be used in the bubble-column condenser; and theconfiguration of those stages can be readily altered). Further still,other aspects, functions and advantages are also within the scope of theinvention; and all embodiments of the invention need not necessarilyachieve all of the advantages or possess all of the characteristicsdescribed above. Additionally, steps, elements and features discussedherein in connection with one embodiment can likewise be used inconjunction with other embodiments. The contents of references,including reference texts, journal articles, patents, patentapplications, etc., cited throughout the text are hereby incorporated byreference in their entirety; and appropriate components, steps, andcharacterizations from these references optionally may or may not beincluded in embodiments of this invention. Still further, the componentsand steps identified in the Background section are integral to thisdisclosure and can be used in conjunction with or substituted forcomponents and steps described elsewhere in the disclosure within thescope of the invention. In method claims, where stages are recited in aparticular order—with or without sequenced prefacing characters addedfor ease of reference—the stages are not to be interpreted as beingtemporally limited to the order in which they are recited unlessotherwise specified or implied by the terms and phrasing.

What is claimed is:
 1. A method for multi-stage bubble-column vapormixture condensation using a multi-stage bubble-column vapor mixturecondenser, comprising: at least a first stage and a second stage,wherein each stage includes: a carrier-gas inlet; a carrier-gas outlet;and a condenser chamber containing a condensing bath in fluidcommunication with the carrier-gas inlet and the carrier-gas outlet,wherein the carrier-gas inlet is positioned to bubble carrier gas fromthe carrier-gas inlet up through the condensing bath, overcoming ahydrostatic head of the condensing bath, wherein the carrier-gas outletis positioned with an opening for carrier-gas extraction above thecondensing bath, wherein the first-stage carrier-gas outlet is in fluidcommunication with the carrier-gas inlet of the second stage tofacilitate flow of the carrier gas through the condensing bath in thecondenser chamber of the first stage and then through the condensingbath in the condenser chamber of the second stage, and wherein thecondenser chamber is configured with a height-to-diameter aspect ratio,an orientation angle, and is sufficiently free of impediments toestablish a natural and regular liquid circulation loop in thecondensing bath that maintains a temperature difference of no greaterthan 1%, measured in Kelvin, from top-to-bottom of the bath, the methodcomprising: introducing a carrier gas including a vaporized componentthrough the carrier-gas inlet of the first stage; bubbling the carriergas up through the first-stage condensing bath while condensing aportion of the vaporized component of the carrier gas into thefirst-stage condensing bath; extracting the carrier gas from thecarrier-gas outlet of the first stage; passing the carrier gas from thecarrier-gas outlet of the first stage through the carrier-gas inlet ofthe second stage; bubbling the carrier gas up through the condensingbath of the second stage while condensing an additional portion of thevaporized component of carrier gas into the second-stage condensingbath; extracting the carrier gas from the carrier-gas outlet of thesecond stage; and establishing the natural and regular liquidcirculation loop in each condensing bath to thereby maintain thetemperature difference of no greater than 1%, measured in Kelvin, fromtop-to-bottom of each bath.
 2. The method of claim 1, wherein thecondensing bath in the first stage is at least 5° C. warmer than thecondensing bath in the second stage.
 3. The method of claim 1, furthercomprising adding the vaporized component to the carrier gas byvaporizing the vaporized component from a feed liquid into the carriergas in a humidifier.
 4. The method of claim 3, wherein the vaporizedcomponent is water.
 5. The method of claim 4, wherein the condensingbath in each stage consists essentially of water, and the method furthercomprising extracting the water from the condensing baths.
 6. The methodof claim 1, wherein the carrier gas is extracted from the carrier-gasoutlet of each stage with a concentration of vaporized component that islower than that of the carrier gas as it entered the stage.
 7. Themethod of claim 1, further comprising transferring the carrier gasthrough an intermediate exchange conduit between intermediate stages ofthe bubble-column vapor mixture condenser and of the humidifier.
 8. Themethod of claim 1, further comprising directing coolant through aninternal conduit in counterflow to carrier-gas flow through thecondenser chamber and recovering energy from condensation with thecoolant.
 9. The method of claim 8, wherein the coolant is in a liquidphase.
 10. The method of claim 9, wherein the coolant includes water.11. The method of claim 1, wherein the condensing bath has aheight-to-diameter aspect ratio less than 0.5.